This invention relates to a one-revolution stop mechanism for a dispenser and a dispensing method for rolled web material of the flexible sheet type such as paper toweling. The stop mechanism has a low operating force and is associated with the feed roller in the dispenser to allow the feed roller to undergo one revolution and then be stopped in dispensing an individual sheet of the rolled weld material.
Dispensers for rolled flexible sheet material, such as paper toweling, are well-known in the art and many of these dispensers include mechanisms for perforating or severing a web of material to divide the web into individual sheets. Towel dispensers have also been developed with various mechanisms or techniques to provide a waste-restricting system, namely, the dispenser permits only a single individual sheet to be dispensed to the intending user at one time with a delay being provided before the user can gain access to a second individual sheet.
For sanitary reasons, towel dispensers in public washrooms should preferably be operable by merely pulling down on an exposed portion of the towel weld with no need to touch parts of the dispenser such as cranks, buttons or levers commonly present in many prior art types of towel dispensers, these actuators serving to activate the towel dispenser in supplying the length of towel web or individual toweling sheets.
At the same time, for the sake of economy, the dispenser should eliminate unnecessary waste of paper toweling while still not unduly restricting use of the toweling to the intending user. Certain dispensers now on the market accomplish these objectives by such devices as spring-operated one-revolution stop feeding mechanisms and vacuum cup timers. Spring-operated devices have the disadvantage that in being cocked while the towel is being withdrawn from the dispenser, a substantial drag is placed on the web of paper toweling, often resulting in it being prematurely torn where it is held by the wet fingers of the intending user. Prior art vacuum cup timers provide the needed time delay between withdrawal of individual towel sheets to thus reduce waste but have the disadvantage that the desired preset time intervals cannot be reliably maintained especially at very short time interval settings.
In addition, in paper towel dispensers where the towel web is severed or perforated internally, a device must be provided to prevent the premature separating of individual towels from the following web as it uncoils from the supply roll of toweling. Strong, thus, harsh, paper toweling is therefore required.
FIG. 1 represents one example of a towel dispenser known in the prior art. The dispenser 30 has a cabinet 31 adapted to be mounted at a convenient location for intending users of the paper toweling supplied from the rolled web material carried within the cabinet 31. A portion of the cabinet 31 is broken away to display a portion of the one-revolution stop mechanism and other components mounted within the cabinet 31.
A roll 1 of flexible web material is mounted on a yoke 33, the yoke being pivoted at 34 to the backplate of the dispenser cabinet 31. Yoke 33 has a pair of yoke arms with cups 32 rotatably mounted at the outer ends of the yoke arms, these cups being inserted at each core end into the central tubular core of the towel roll 1. With this rather conventional mounting for roll 1, due to gravity the roll rests against the backplate of cabinet 31 to provide a slight braking action and prevent overspinning of the roll when the paper towel web is being removed.
The web W withdrawn from roll 1 is threaded counterclockwise around a pinchroller 3. The web then passes clockwise around the rearside of a feed roller 4 to pass counterclockwise over an exit pinchroller 24. Pinchrollers 3 and 24 are pressed against the feed roller 4 by springs (not shown) with all rollers being supported by appropriate bearings (not shown) in the sideplates of the dispenser cabinet 31. The web W then exits through opening 26 in cabinet 31 to be accessible to intending users of the paper toweling material coming from roll 1. Preferably a tab length T of the toweling web W of about 3 inches will extend outside the dispenser beyond opening 26 to be available for grasping by the intending users of the web material. This preferred length T of web material is automatically fed from the dispenser 30 in conjunction with the operation of a one-revolution stop mechanism.
The feed roller 4 has an internal knife 40 which is mounted laterally offset from the rotational axis of feed roller 4. Knife 40 is supported within the feed roller to project through an opening (not shown) in the feed roller periphery to essentially sever the web material when it passes over the feed roller surface as the feed roller 4 makes a single revolution. The web material is thus perforated to leave only, for example, three uncut 1/4 inch long tabs connecting successive sheets in the web. This transverse perforating of the web material in cabinet 31 defines individual sheets which are of a length equal to the feed roller circumference so that the web W is formed with a row of perforations between one sheet and the next succeeding sheet.
Details of the mounting and operating mechanism for the cutting knife 40 are not shown but the construction may be of the sliding cutter construction disclosed in U.S. Pat. No. 4,712,461.
Feed roller 4 is rotatably mounted on shaft 32 which extends through an appropriate bearing which is carried by the sidewall of cabinet 31. Shaft 32 extends outwardly beyond the bearing and has a feed wheel 36 fixedly secured to R outer end. The feed wheel 36 has a control tab 38 which cooperates with a stop lever 41 to constitute the active components of the stop mechanism as described in allowed and commonly assigned application Ser. No. 838,799 (now U.S. Pat. No. 5,275,446).
U.S. Pat. No. Re 28,911 discloses the use of a conventional vacuum cup timer to provide a time delay between withdrawal of individual towel sheets. The operation of this type of timer will be explained with reference to FIGS. 2 and 3 which are taken from FIG. 10 of the U.S. Pat. No. Re. 28,911.
FIG. 2 is a side elevational view of the one-revolution stop mechanism in an unlatched position as used in the dispenser disclosed in the U.S. Pat. No. Re. 28,911. The mechanism includes a feed wheel 240 which is drive by the towel web being pulled from the dispenser. The mechanism also includes a stop lever 230 which pivots about pivot pin 232. Stop lever 230 has a cam follower 234 and a stop lug 236 which engage camming pin 238 formed on feed wheel 240.
As shown in FIG. 2, cam follower 234 is positional in the rotational path of camming pin 238. The rotation of feed wheel 240 causes camming pin 238 to engage the underside of cam follower 234, raising cam follower 234 upwardly. Stop lever 230, thus, pivots in a clockwise direction about pivot pin 232. As stop lever 230 pivots, vacuum cup 242 is drawn into vacuum-gripping relationship with vacuum cup 244. As feed wheel 240 continues to rotate, camming pin 238 passes under and out of engagement with cam follower 234 to arrive at the position shown in FIG. 3. In this position, vacuum cups 242 and 244 are in full vacuum-gripping relationship and stop lug 236 is in engagement with camming pin 238. The vacuum-gripping force of vacuum cups 242 and 244 maintain stop lever 230 in the position shown in FIG. 3, thus preventing further rotation of feed wheel 240 due to the engagement of camming pin 238 with stop lug 236. The arrested motion of feed wheel 240 results in increased pulling force on the towel which permits an individual sheet of paper toweling to be torn from the web along preformed perforations.
Vacuum cups 242 and 244 remain in vacuum-gripping relationship for a predetermined period of time which is regulated by needle valve 254. Needle valve 254 allows a controlled flow of ambient air into the vacuum environment between vacuum cups 242 and 244 in order to regulate the period of time during which the cups remain in vacuum-gripping relationship. After the vacuum-gripping relationship is destroyed by the entry of ambient air between vacuum cups 242 and 244, stop lever 230 is returned to its unlatched position as shown in FIG. 2 by spring 256 for the start of another cycle.
Though vacuum cup timers perform their intended function, they suffer from a number of disadvantages. As mentioned above, the desired preset time delay interval cannot be reliably maintained, especially at very short time interval settings. Another such disadvantage is that a relatively large amount of compression force is required in order to engage the vacuum cups in a vacuum-gripping relationship. Creation of such a large force also creates a corresponding drag on the towel web, often resulting in premature tearing of the towel. This particular disadvantage is addressed in the U.S. Pat. No. Re. 28,911 patent by making one cup of a relatively hard resilient material and the other of a relatively soft resilient material. The use of a soft resilient material also provides a better cushion for absorption of forces generated by the abrupt arresting of feed wheel movement, thus minimizing wear of the stop mechanism components.
Though the use of resilient material for one of the vacuum cups presents a solution to the high compression force problem, other problems are created. For example, manufacturing cost are increased due to the need to fabricate cups from two different materials. There are obvious economies to be realized if both cups are of the same design and material. In addition, reducing the hardness of the vacuum cups also reduces the vacuum-gripping force between the cups.